JP2740825B2 - Thermal recording sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording sheet used in the fields of facsimile, printer and the like, and more particularly to a heat-sensitive recording sheet for security protection.

[0002]

2. Description of the Related Art In recent years, various recording systems have been used in the fields of facsimile machines, printers, and the like. In particular, thermosensitive recording has been actively used because of its simplicity. As shown in FIG. 4, the heat-sensitive recording sheet used for this heat-sensitive recording is composed of a colorless or light-colored leuco dye such as crystal violet lactone on a support 1 and an acidic substance such as phenol which forms a color when heated. It is generally known that a thermosensitive recording layer 2 containing a hydrophilic compound or the like is formed. In order to perform thermal recording, the thermal recording layer is heated by a thermal head 5 that selectively develops color in accordance with the recording information to partially develop color to perform thermal recording.

[0003] Information transmission systems using such a recording system have been remarkably widespread because of their convenience. However, there is no sufficient countermeasure in terms of confidentiality, and there is an extremely high risk of leakage of important confidential information. There is a demand for a recording system in which it is difficult for three persons to read with the naked eye, and furthermore, copying by a copying machine is not possible, and furthermore, only a specific person can read out recorded information easily as needed.

Japanese Unexamined Patent Publication No. 62-14163 discloses a technique for the purpose of protecting such security, and discloses a dry toner containing a leuco dye, a developer and a desensitizer, and an image formed thereby. 3 shows a forming method. However, the image formed by this dry toner does not become completely colorless, so it can be read, and when reading, it must be kept in a heated state, so that the image can be fixed due to reversibility. However, when it is necessary to read again, there is the inconvenience that the reading must be performed again in the heated state.

[0005]

DISCLOSURE OF THE INVENTION The present invention is a heat-sensitive device which is difficult to read by a third party, cannot be copied, and can be easily read only by a specific person if necessary. It is intended to provide a recording sheet.

[0006]

In order to achieve the above object, the present invention relates to a heat-sensitive recording sheet having a heat-sensitive recording layer, which is colored by heating, formed on a support. The present invention provides a heat-sensitive recording sheet characterized by having a layer whose transparency changes reversibly, is opaque even after color recording by heating, and becomes transparent by heating at a color recording temperature or lower.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A security thermosensitive recording sheet according to the present invention has a configuration in which a recorded information cannot be read by a third party at all until the recorded information is visualized by a specific person. As shown in FIG. 1, a thermosensitive recording layer 2 composed of a color-forming substance and a color-developing substance is formed on a support 1, and a layer 3 whose transparency reversibly changes depending on the temperature is provided thereon. A solvent-resistant layer 4 is provided as required.

[0008] transparency depending on the characteristic temperature in the present invention is explained by drawings a layer 3 that changes reversibly, the heat sensing element 2 is in the cloudy opaque state at room temperature, for example T ₀ or less. When it is heated to a temperature between T _{1 and} T ₂ , it becomes transparent, and in this state, it remains transparent even if it is returned to room temperature below T ₀ . Further heating to T ₃ or more temperature becomes translucent state intermediate between the maximum transparency and the maximum opacity. Next, when the temperature is lowered, the state returns to the original cloudy and opaque state without taking the transparent state again. It should be noted that when this opaque state is heated to a temperature between T _{1 and} T ₂ and then cooled to room temperature, that is, to a temperature equal to or lower than T _0, it can be in a transparent state. Furthermore, the, those became clear at room temperature also again heated to T ₃ or higher, by returning to room temperature, return to the cloudy opaque state again.

Therefore, the object of the present invention can be achieved by using such a layer whose transparency reversibly changes depending on the temperature.

The recording process will be described sequentially with reference to FIG.
(A) is a configuration of the heat-sensitive recording sheet of the present invention.
A thermosensitive recording layer 2 made of a color-forming substance and a color-developing substance is formed thereon, and a layer 3 whose transparency reversibly changes depending on the temperature is provided thereon. At T ₀ or less), 3 is opaque. Next, (FIG. 3 (b)
In the state at the time of recording, by the thermal head 5 selectively heat according to the recording information, which was subjected to thermal recording by color thermosensitive recording layer by heating at T ₃ or more temperatures Figure 3, at ambient temperature (T ₀ following figure 3) 3 is opacified, recording information, in order to not be read by a third party, the security of information is maintained. In addition, copying by a copying machine is impossible due to opacity. Next, FIG.
(C) is a process for a specific person to see the record information,
Figure 3 T ₁ through T ₂ in FIG. 3 A thermosensitive recording sheet obtained in (b)
Heated to a temperature between normal temperature, i.e. when the T ₀ temperature below, the opaque layer changes to a transparent layer can be seen a clear record information. Further, copying by a copying machine or the like can be performed without any trouble.

In the present invention, the color-forming substance used in the heat-sensitive recording layer is not particularly limited, and those conventionally used for heat-sensitive materials can be arbitrarily applied, but colorless or pale-colored leuco dyes may be used alone or in combination of two or more. It is good to use it.

Such leuco dyes include, for example,
Leuco compounds of dyes such as triphenylmethane, fluoran, phenothiazine, auramine and spiropyran are preferably used. Specific examples of such leuco dyes include, for example, those shown below.

3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis ( p-dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6 -Chlorofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluoran, 3-diethylamino-7,8-benzfluoran, 3-diethylamino-6-methyl-7-chlorofluoran 3- (Np-tolyl-N-ethylamino) -6-methyl-7-anili Nofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluoran, 2- {3,6-bis (diethylamino) ) -9- (o-Chloroanilino) xanthyl lactam benzoate , 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3- Dibutylamino-7- (o-chloroanilino) fluoran, 3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluoran, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3- (N, N-diethylamino ) -5-Methyl-7-
(N, N-dibenzylamino) fluoran, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrrospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrrospirane, 3- ( 2'-hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5'-chlorophenyl)
Phthalide, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5'-nitrophenyl)
Phthalide, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5'-methylphenyl)
Phthalide, 3- (2'-methoxy-4'-dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-
Methylphenyl) phthalide, 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7-trifluoromethylanilinofluoran, 3-diethylamino-5-chloro-7- (N -Benzyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluoran, 3-diethylamino-5-chloro-7- (α-phenylamino) fluoran, 3- (N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluoran, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluoran, 3-diethylamino-5-methyl-7- (α- Phenylethylamino) fluoran, 3-diethylamino-7-piperidinofur Run, 2-chloro-3-(N-Mechirutoruijino)-7-(p
-N-butylanilino) fluoran, 3- (N-benzyl-N-diclohexylamino)-
5,6-benzo-7-α-naphthylamino-4′-bromofluoran, 3-diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluoran and the like.

In the present invention, if necessary, a heat-fusible substance may be added. Specific examples thereof include dimethyl terephthalate, dimethyl 5-hydroxyphthalate, acenaphthene, dimethylnaphthalene, and the like.
Examples include dibenzofuran and 9-fluorene.

Specific examples of the color developing substance which causes the color forming substance to develop a color by heating include the following.

Gallic acid, salicylic acid, 3-isopropylsalicylic acid, 3-cyclohexylsalicylic acid, 3,5-
Di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4′-isopropylidene diphenol, 4,4′-isopropylidenebis (2-
Chlorophenol), 4,4′-isopropylidenebis (2,6-dibromophenol), 4,4′-isopropylidenebis (2,6-dichlorophenol),
4′-isopropylidenebis (2-methylphenol), 4,4′-isopropylidenebis (2,6-dimethylphenol), 4,4′-isopropylidenebis (2-tert-butylphenol), 4,4 ′ -Se
c-butylidene diphenol, 4,4′-cyclohexylidenebisphenol, 4,4′-cyclohexylidenebis (2-methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α -Naphthol, β-naphthol,
3,5-xylenol, thymol, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, novolak-type phenol resin, 2,2′-thiobis (4,
6-dichlorophenol), catechol, resorcinol,
Hydroquinone, pyrogallol, phloroglysin, phloroglysin carboxylic acid, 4-tert-octylcatechol, 2,2′-methylenebis (4-chlorophenol), 2,2′-methylenebis (4-chlorophenol), 2,2′- Methylene bis (4-methyl-6-te
rt-butylphenol), 2,2'-dihydroxydiphenyl, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-hydroxybenzoic acid-p-chloro Benzyl, p-hydroxybenzoic acid-o-chlorobenzyl, p-hydroxybenzoic acid-p
-Methylbenzyl, p-hydroxybenzoic acid-n-octyl, benzoic acid, zinc salicylate, 1-hydroxy-2
-Naphthoic acid, 2-hydroxy-6-naphthoic acid, 2-
Hydroxy-6-naphthoic zincate, 4-hydroxydiphenylsulfone, 4-hydroxy-4′-chlorodiphenylsulfone, bis (4-hydroxyphenyl) sulfide, 2-hydroxy-p-toluic acid, 3,5-di-
tert-butyl zinc salicylate, 3,5-di-ter
tin t-butylsalicylate, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, boric acid and the like.

The layer whose transparency changes irreversibly depending on the temperature is mainly composed of an organic low-molecular substance dispersed in a resin base material. Preferred resins include polyvinyl chloride and vinyl chloride. -Vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-acrylate copolymer, etc .; vinylidene chloride; chloride Vinylidene chloride-vinyl copolymer; vinylidene chloride-based copolymer such as vinylidene chloride-acrylonitrile copolymer; polyester; polyamide; polyacrylate or polymethacrylate or acrylate-methacrylolate copolymer; silicone resin. These may be used alone or as a mixture of two or more.

On the other hand, the organic low-molecular substance has a temperature T _0-
It may be appropriately selected according to selection of T _3, but 3
Those having a temperature of about 0 to 200 ° C, particularly about 50 to 150 ° C, are preferred. Such organic low molecular weight substances include alkanols;
Alkane diols; halogen alkanols or halogen alkane diols; alkyl amines; alkanes; alkenes; alkynes; halogen alkanes; halogen alkenes; halogen alkynes; cycloalkanes; cycloalkenes; cycloalkynes; Amides or ammonium salts; saturated or unsaturated halogen fatty acids or their esters, amides or ammonium salts; allyl carboxylic acids or their esters, amides or ammonium salts; halogen allyl carboxylic acids or their esters, amides or ammonium Salts; thioalcohols; thiocarboxylic acids or their esters, amides, or ammonium salts; It is. These can be used alone or 2
Used as a mixture of more than one species. These compounds have 10 to 60 carbon atoms, preferably 10 to 38 carbon atoms, particularly preferably 10 to 30 carbon atoms. The alcohol group in the ester may be saturated or unsaturated, and may be halogen-substituted. In any case, the organic low molecular weight substance contains at least one of oxygen, nitrogen, sulfur and halogen in the molecule, for example, -OH, -COOH, -CONH, -COOR,-
_{NH -, - NH 2, -S} -, - S-S -, - O-, it is preferably a compound containing a halogen and the like.

More specifically, these compounds include lauric acid, dodecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, stearic acid, behenic acid, nonadecanoic acid,
Higher fatty acids such as arachiic acid and oleic acid; esters of higher fatty acids such as methyl stearate, tetradecyl stearate, octadecyl stearate, octadecyl laurate, tetradecyl palmitate and docosyl behenate. Examples of the solvent include organic solvents such as tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, and benzene.

The weight ratio of the organic low-molecular substance and the resin base material in the heat sensitive material is preferably about 1: 0.5 to 1:16. When the ratio of the resin base material is less than this, it is difficult to form a film in which the organic low-molecular substance is held in the resin base material. Becomes difficult.

When a layer whose transparency changes reversibly depending on the temperature is provided on the heat-sensitive recording layer, an organic solvent is used. It is necessary to provide a solvent-resistant layer on the heat-sensitive recording layer. As the solvent-resistant layer, a water-soluble resin layer is preferable, and for example, polyvinyl alcohol, hydroxyethylcellulose, methylcellulose, ethylcellulose, polyvinylpyrrolidone, polyacrylamide, polyvinylacetate and the like can be used.

[0022]

Next, the present invention will be described in detail with reference to examples.
In the following, all parts and percentages are based on weight.

Example 1 [Solution A] 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilinofluorane 10 parts 10% aqueous solution of hydroxyethylcellulose 10 parts Water 30 parts [Solution B] Dimethyl 5-hydroxyphthalate 30 parts 10% aqueous solution of hydroxyethyl cellulose 30 parts Water 90 parts [Solution C] 4,4'-isopropylidene diphenol 10 parts Calcium carbonate 30 parts Methyl cellulose 5% aqueous solution 40 parts Water 120 parts to a solution obtained, B liquid and C liquid were mixed, dry coverage in high quality paper with a basis weight of 50 g / m ² is 5 g /
A thermosensitive color-forming layer was formed by applying and drying so as to obtain m ^2, and a 5% aqueous solution of polyvinyl alcohol was applied and dried as a solvent-resistant layer thereon. Next, a component composed of 5 parts of stearic acid, 20 parts of vinyl chloride-vinyl acetate copolymer (VYHH manufactured by UCC), 25 parts of toluene, and 50 parts of tetrahydrofuran were mixed and uniformly dissolved, and the mixture was coated with a wire bar. An opaque layer having a thickness of 50 μm was provided. The heat-sensitive recording sheet produced as described above was in an opaque state. When information was recorded at 200 ° C. using a thermal head using this, the recorded information could not be read at room temperature because the surface was opaque. When this was heated to 60 ° C., the surface became transparent, clear black print appeared, and remained transparent even when cooled to room temperature. Until heated to 60 ° C., copying by a copying machine could not be performed.

Example 2 [Solution A] Crystal violet lactone 10 parts 10% aqueous solution of methylcellulose 10 parts Water 30 parts [Solution B] dimethyl terephthalate 30 parts 10% aqueous solution of methylcellulose 30 parts Water 30 parts [Solution C] p- Benzyl hydroxybenzoate 10 parts Calcium carbonate 30 parts Methylcellulose 5% aqueous solution 40 parts Water 120 parts The liquid A, liquid B and liquid C obtained as above are mixed and dried on a high-quality paper having a basis weight of 50 g / m ^2. 6g /
A thermosensitive color-forming layer was formed by applying and drying so as to obtain m ^2, and a 5% aqueous solution of polyvinyl alcohol was applied and dried as a solvent-resistant layer thereon. Next, 5 parts of behenic acid, 20 parts of vinyl chloride-vinyl acetate copolymer (VYHH manufactured by UCC), 75 parts of tetrahydrofuran were mixed and uniformly dissolved, and the mixture was coated with a wire bar. An opaque layer was provided. When recording was performed on the heat-sensitive recording sheet produced as described above in the same manner as in Example 1, sufficient confidentiality was maintained, and deep blue prints appeared clearly by visualization. Further, when this product was heated to 130 ° C., the entire surface developed a blue color, and the recorded information could not be read at all, and could be processed without cutting by a shredder.

[0025]

As described above, since the heat-sensitive recording sheet according to the present invention is provided with a layer whose transparency reversibly changes depending on the temperature, it is difficult for a third party to read the sheet and it is impossible to copy. In addition, there is a unique effect that only a specific person can easily read recorded information as needed. Further, for example, if the heat-sensitive recording sheet according to the present invention is used as a material for cards such as prepaid cards and credit cards, train tickets, buses, subway tickets, coupons or commuter passes, the falsification of these cards etc. This has many advantages such as prevention of traffic accidents and illegal acts such as illegal riding.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the configuration of an embodiment of a thermosensitive recording sheet according to the present invention.

FIG. 2 is an explanatory diagram of the principle of a layer whose transparency reversibly changes depending on temperature.

FIG. 3 is an explanatory diagram of a recording step of the thermosensitive recording sheet of the present invention.

FIG. 4 is a cross-sectional view of a configuration of a conventional heat-sensitive recording sheet.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 support 2 thermosensitive recording layer 3 layer whose transparency changes reversibly depending on temperature 4 solvent resistant layer 5 thermal head

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B41M 5/18 E B41J 3/20 109E

Claims (1)

(57) [Claims] In a heat-sensitive recording sheet having a heat-sensitive recording layer which develops color by heating formed on a support, transparency reversibly changes on the above-mentioned recording layer depending on temperature, and opaque even after color-forming recording by heating. A heat-sensitive recording sheet provided with a layer which becomes transparent by heating at a color-forming recording temperature or lower.